In this study postmenopausal women will have baseline markers of bone metabolism including serum calcium, phosphate, alk phos, sodium, potassium, creatinine, chloride, osteocalcin, PTH, and calcitriol, and 24-hour urine sodium, calcium, deoxypyridinoline, creatinine, potassium, and cyclic AMP. The women will then be adapted to a low salt diet for four weeks and these outcomes repeated. Then they will be randomized to a high salt diet with placebo or a high salt diet with potassium bicarbonate for four weeks and the outcomes repeated.